Buffer overflow creating 92 drive RAID60 array

Tim Nufire linux-poweredge_tim at ibink.com
Fri Mar 9 16:13:07 CST 2012


Thanks to everyone that responded on this issue!!

It turns out that the buffer overflow only effect the command line version of Open Manage and I was able to create my volume via the Web UI. With regard to configuration, I'm creating the array with 4 spans of 23 drives each so reliability and performance should both be good.

Again, thanks for all the suggestions.

Tim

On Mar 7, 2012, at 10:32 AM, Steff wrote:

> On 7 March 2012 18:04, John Lloyd <jal at mdacorporation.com> wrote:
>> 
>> Based on my understanding, a RAID-60 array would mean two independent RAID-6 arrays with blocks interleaved (RAID-0).  Each RAID-6 array would be 46 disks, 2 of which are parity.  44 disks would be striped in parallel, with parity calculated on a 128kbyte stripe size.
>> 
>> The unit of a stripe would be 128kB multiplied by 44 = about 5 megabytes of data.  This would not be so much of a problem but the 44 disks would be.  Each write (such as an inode update) would require 44 physical reads (assuming parity matches) and 46 physical writes.  Caching might help a bit but basically you would be waiting for 90+ physical IOs per logical update.
>> 
>> In my own experience the largest useful RAID set size is 8 data disks plus parity.   If 8 disks are not big enough then stripe and/or concatenate them with LVM or RAID-0 in your RAID controller or whatever.
> 
> I'm not sure that's wholly true. RAIDn0 means striping over a number
> of RAIDns, not necessarily just two. One of the things I'd hope for
> from a commercial RAID controller would be selecting the size of the
> pools within a sensible maximum (based on intimate knowledge of what
> the controller is capable of) and increasing the number to match. That
> said, as I mentioned to the original poster, I'd be tempted just to
> create the RAID6s individually and use md to stripe over them. I think
> LVM2 will do striping too.
> 
> S
> 
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